The production of an electric arc is central to the operation of arc welders and plasma arc torches. Arc welders and plasma arc torches include a power supply that creates a potential difference between an electrode and a workpiece so that an electric arc is produced between the electrode and the workpiece.
Arc welders are used for joining metal workpieces and can be generally categorized into three basic types; manual "stick electrode" arc welders, MIG welders and TIG welders. With conventional stick electrode arc welding, a consumable coated rod or stick of metal, which functions as the anode, is placed adjacent to the workpiece being welded, which functions as the cathode. An arc is generated between the anode and the workpiece to form a weld bead and join the workpiece to another workpiece. The heat of the arc transfers filler metal from the anode to the workpieces to form the weld bead. After the anode has been consumed, it must be replaced with a new anode. MIG (Metal-Inert Gas) welding is similar, except that an inert or slightly oxidizing gas is supplied to shield the arc from the atmosphere and improve the metallurgical qualities of the weld. TIG (Tungsten-Inert Gas) welding is similar to MIG welding, except a non-consumable tungsten anode is used. Filler material may be supplied by way of an adjacent consumable rod.
Plasma arc torches are commonly used for cutting, welding, surface treating, melting, or annealing a metal workpiece. Such working of the workpiece is facilitated by a plasma arc that extends from the plasma arc torch to the workpiece. The plasma arc is formed by introducing a gas to an electrical arc extending between the plasma arc torch and the workpiece, such that the electrical arc ionizes the gas to create the plasma arc.
The power supply of an arc welder or a plasma arc torch typically includes an input line that is connected to a conventional supply of electric power, such as household or industrial alternating current. The power supply also includes two output terminals. One of the terminals is electrically connected to an anode, such as by way of an electrode holder, and the other of the terminals is connected to the workpiece to produce an electric arc between the anode and the workpiece. The power supply typically includes a housing that contains the various electrical components of the power supply. The housing typically includes one or more cover panels that shield the electrical components from the operator.
Some of the electrical components of the power supply can generate large amounts of heat. Accordingly, many conventional power supplies include a cooling fan that forces air through the power supply to cool the electrical components. It is common in such power supplies for heat sinks that are connected to electrical components to be elongate and thereby define a longitudinal axis. It is also common for the cooling fan to define a flowpath with a flow axis, and for the flow axis to be parallel to the longitudinal axis. As a result, the flow of air through the power supply is parallel to the cooling surfaces of the heat sinks and can be utilized to cool one or more heat dissipating components downstream from the heat sinks. Advances in power supply design, such as power, size, etc., often demand greater and greater heat removal capabilities.
However, it has been discovered that cooling flow that is parallel to a surface being cooled such as in the conventional power supplies discussed above is not as effective at removing heat as a cooling flow that is perpendicular to, and thereby fully impinging upon, the surface being cooled. For example, a flow of air directed perpendicularly to a finned surface of a heat generating device (that is, fully-impinging airflow) removes more heat than a flow of air directed parallel to the fins. However, it can be difficult or inefficient for fully-impinging airflow to be effectively used to cool components that are distant from the component receiving the fully-impinging airflow. For example, it is common for a fully-impinging airflow to define a single flow axis upstream from the component receiving the fully-impinging airflow. However, the flow of air is subsequently dispersed typically in various directions and therefore is difficult to use for the purpose of directing a substantial portion of the airflow toward another component to be cooled.
Thus, conventional power supplies are limited in the amount of heat removal possible because of the use of a cooling airflow parallel to the longitudinal axes of the heat sinks. However, it has not previously been feasible to stray from the parallel airflow design because of the desire to also cool downstream components with the cooling airflow. Accordingly, there is a great need in the industry for a power supply having improved airflow cooling relative to conventional power supplies which allows for the cooling of downstream components.